EMF and Torque Production MCQ

Test your knowledge with important EMF and Torque Production MCQ and their applications. These MCQs are beneficial for competitive exams too. Explore 30 + more EMF and Torque Production MCQs at Bissoy

• For an ideal DC machine, which phenomenon will reduce the terminal voltage?
  ক

  Armature reaction

  খ

  Commutation

  গ

  Armature ohmic losses

  ঘ

  All will contribute in reducing the terminal voltage
• For a constant emf, if field current is reduced then the speed of the DC motor will_____
  ক

  Remains same

  খ

  Increases

  গ

  Decreases

  ঘ

  Can’t say
• In a DC machine, what is the torque induced beyond the pole shoes?
  ক

  0

  খ

  2/π *∅*i

  গ

  π *∅*i/2

  ঘ

  Can’t be calculated
• A 4-pole wave wound DC motor drawing an armature current of 20 A has provided with 360 armature conductors. If the flux per pole is 0.015 Wb then the torque developed by the armature of motor is _______
  ক

  10.23 N-m

  খ

  34.37 N-m

  গ

  17.17 N-m

  ঘ

  19.08 N-m
• If the average coil emf of a DC motor is doubled and flux is halved (keeping other parameters constant) then its shaft speed will become ___________
  ক

  Twice of the original speed

  খ

  Square of the original speed

  গ

  Four times of the original speed

  ঘ

  Half of the original speed
• If the no load speed of DC motor is 1300 rpm and full load speed is 1100 rpm, then its voltage regulation is ____________
  ক

  12.56%

  খ

  18.18 %

  গ

  17.39%

  ঘ

  18.39%
• Coil torque for 20 kA armature current (T1) and 40 mA armature current (T2), will have ratio T1/T2=____ (assuming all other parameters same for both machines).
  ক

  1/2

  খ

  2/1

  গ

  1/4

  ঘ

  4/1
• A 4-pole Dc wound machine is lap wound with 400 conductors. The pole shore is 20 cm long and average flux density over one-pole pitch is 0.4 T, the armature diameter being 30 cm. What is the value of induced emf?
  ক

  188 V

  খ

  276 V

  গ

  94 V

  ঘ

  188 mV
• A 4-pole Dc wound machine is lap wound with 400 conductors. The pole shore is 20 cm long and average flux density over one-pole pitch is 0.4 T, the armature diameter being 30 cm. What is the value of flux/pole?
  ক

  0.188 Wb

  খ

  18.88 Wb

  গ

  0.0188 Wb

  ঘ

  1.888 Wb
• What is the value of pole pitch (in SI unit) for mean air gap radius= 0.5mm and P=4?
  ক

  0.785* 10-6

  খ

  0.785* 10-3

  গ

  0.785* 10-2

  ঘ

  0.785* 10-4
• 9.What is the torque equation in terms of B, Ic, l, Zr (r= mean air gap radius)?
  ক

  Bav*Ic*l*Zr

  খ

  Bav*Ic*l/Zr

  গ

  Bav*Ic*Zr/l

  ঘ

  Can’t be expressed
• What is the value of Np in an average coil emf equation, for 10 armature conductors with 2 parallel paths?
  ক

  2

  খ

  3

  গ

  2.5

  ঘ

  4
• Emf and torque produced in a DC machine are proportional to ________ and _________ respectively.
  ক

  Armature speed and armature emf

  খ

  Armature emf and armature speed

  গ

  Armature current and armature emf

  ঘ

  Armature speed and armature current
• What is the average coil emf generated in a 4-pole DC machine having flux/pole equal to 0.1 wb rotating at 1500 rpm? (No. of coil sides = 100)
  ক

  19 kV

  খ

  1.9 kV

  গ

  190 V

  ঘ

  19 V
• Average coil emf for 20 coil turns (E1) and 40 coil turns (E2), will have ratio E1/E2=____ (assuming all other parameters same for both machines).
  ক

  1/2

  খ

  2/1

  গ

  1/4

  ঘ

  4/1
• Emf produced by DC machine, for zero armature current (E1) and non-zero armature current (E2) can be related as__________
  ক

  E1 = E2

  খ

  E1 > E2

  গ

  E1 < E2

  ঘ

  Can’t be determined
• In a DC machine, average energy stored in the magnetic field remains constant independent of the armature rotation.
  ক

  True

  খ

  False
• Nature of the flux density wave in the air gap is__________ (for armature current equal to 0)
  ক

  Flat topped with quarter wave symmetry

  খ

  Point topped with quarter wave symmetry

  গ

  Flat topped with half wave symmetry

  ঘ

  Point topped with half wave symmetry
• In which mode machine is operating, given that conductor current is in the same direction of conductor emf?
  ক

  Motoring

  খ

  Generating

  গ

  Can’t be determined using directions

  ঘ

  In both modes for different cycles